python3 字典update与deepcopy

a = {1:{2:3}}
b= {}
b.update(a)
print(b,1)
a[1][2] = 4
print(b,2)
print(id(a[1]),3)
print(id(b[1]),3)
#结果：
# {1: {2: 3}} 1
# {1: {2: 4}} 2
# 5095520 3
# 5095520 3
#发现这两个前套字典中的内存地址是一个，所以改变一个另一个也改变

#deepcopy
from copy import deepcopy
c = {1:{2:3}}
d = deepcopy(c)
print(d,1)
c[1][2] = 4
print(d,2)
print(id(c[1]),3)
print(id(d[1]),3)
#结果
# {1: {2: 3}} 1
# {1: {2: 3}} 2
# 5750192 3
# 54535776 3
#这里发现两个id是不一样的